1. Field of the Invention
The present invention relates to an imaging device which generates a picture image signal for a picture image for cinema film and a picture image for television which have different frame rates.
Priority is claimed on Japanese Patent Application No. 2004-097486, filed Mar. 30, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
Conventionally, a picture image of a cinema film is photographed at 24frames/second, in order to project such a picture image of a cinema film via television, so called 2-3 pulldown in which two frames of the cinema film are converted into 5 fields is performed. Incidentally, frame rate is the number of pictures which are displayed during one second. In the NTSC (National TV Standards Committee) standard, 525 scan lines are drawn for one frame, this scanning being divided into two interlaced scanning episodes, but a field consists of scanning the even numbered scan lines or the odd numbered scan lines one time. In other words, according to the NTSC standard, a single frame is made up from two fields.
In the following, the 2-3 pulldown method will be explained with reference to FIG. 10. According to the 2-3 pulldown method, a cinema film which is photographed at 24 frames/second is converted into a television signal at 60 fields/second. In 2-3 pulldown, the first frame of the cinema film is converted into a first frame (two fields) of the television signal. Furthermore, the second frame of the cinema film is converted into a total of the second frame (two fields) of the television signal and one field of its third frame. Subsequently, a single frame of the cinema film is converted, alternatingly, into two fields and three fields of the television signal in the same manner.
On the other hand, in order to convert a picture image for television which is photographed at 60 fields/second (=30 frames/second) for cinema film, a so called kinescope recorder method is employed. With this kinescope method, a single frame is extracted from five frames of the television signal, and remaining four frames are converted into four frames of cinema film. FIG. 11 shows this kinescope method. Five frames of the television picture image which is photographed at 60 fields/second are temporally matched to four frames of the cinema film, so that one frame is cut out for every five frames of television signal, thus converting the television image into a cinema film. The above method is described in “All Cinema Production, Basis and Guide to Cinema Production Technology”, (Nobutada Yagi and eight others, Photographic Industry Publishing Corp., 31 Jul. 2000).
Furthermore, although a multi frame rate compliant imaging device which can set any desired value for the frame rate during photography by controlling the drive of an imaging element is considered, since the output is single-standard accordingly the frame rate is fixed to predetermined frame rate during photographic recording.
Therefore, 2-3 pulldown is needed to convert a picture image for a cinema film which is photographed at 24 frames/second during recording into a television signal subsequently, a kinescope is needed to convert the television signal into the picture image of cinema film.